An commonly used industry term, a short form of the proper name, Operational Amplifier. The opamp was originally designed to carry out mathematical operations in analog computers, such as calculating positions and co-ordinates. It however has been found to have numerous other applications. The opamp IC comes in several packages but the most common form is an 8 pin integrated circuit, the most common one being the type 741. They are tremendously popular hobby circuit components. The 741 has two inputs and one output. The input marked with a - sign produces an amplified inverted output. The input marked with a + sign produces an amplified but non inverted output. The opamp requires positive and negative power supplies, together with a common ground although some circuits can be designed to work from a single supply. If the two inputs are joined together, then the output voltage should be exactly midway between the two supply rails, zero volts. If it is not, then there are two connections for adding a potentiometer.